Overdiagnosis in the population-based organized breast cancer screening program estimated by a non-homogeneous multi-state model: a cohort study using individual data with long-term follow-up

• Published in: Breast cancer research : BCR 2018-12, Vol.20 (1), p.153-153, Article 153
• Main Authors: Wu, Wendy Yi-Ying, Törnberg, Sven, Elfström, Klara Miriam, Liu, Xijia, Nyström, Lennarth, Jonsson, Håkan
• Format: Article
• Language: English
• Subjects: Age; Aged; Analysis; Breast cancer; Breast Neoplasms - diagnostic imaging; Breast Neoplasms - epidemiology; Cancer screening; Cohort analysis; Diagnosis; Early Detection of Cancer - methods; Early Detection of Cancer - statistics & numerical data; Estimates; Female; Follow-Up Studies; Health risk assessment; Humans; Invasiveness; Mammography; Mammography - statistics & numerical data; Mass Screening - methods; Mass Screening - statistics & numerical data; Medical Overuse - statistics & numerical data; Medical screening; Medicin och hälsovetenskap; Middle Aged; Mortality; Multi-state model; Organized screening program; Overdiagnosis; Patient Acceptance of Health Care - statistics & numerical data; Population; Population-based studies; Prevalence; Studies; Sweden - epidemiology; Systematic review; Women's health; Womens health
• ISSN: 1465-542X; 1465-5411; 1465-542X
• DOI: 10.1186/s13058-018-1082-z

Overdiagnosis, defined as the detection of a cancer that would not become clinically apparent in a woman's lifetime without screening, has become a growing concern. Similar underlying risk of breast cancer in the screened and control groups is a prerequisite for unbiased estimates of overdiagnosis, but a contemporary control group is usually not available in organized screening programs. We estimated the frequency of overdiagnosis of breast cancer due to screening in women 50-69 years old by using individual screening data from the population-based organized screening program in Stockholm County 1989-2014. A hidden Markov model with four latent states and three observed states was constructed to estimate the natural progression of breast cancer and the test sensitivity. Piecewise transition rates were used to consider the time-varying transition rates. The expected number of detected non-progressive breast cancer cases was calculated. During the study period, 2,333,153 invitations were sent out; on average, the participation rate in the screening program was 72.7% and the average recall rate was 2.48%. In total, 14,648 invasive breast cancer cases were diagnosed; among the 8305 screen-detected cases, the expected number of non-progressive breast cancer cases was 35.9, which is equivalent to 0.43% (95% confidence interval (CI) 0.10%-2.2%) overdiagnosis. The corresponding estimates for the prevalent and subsequent rounds were 15.6 (0.87%, 95% CI 0.20%-4.3%) and 20.3 (0.31%, 95% CI 0.07%-1.6%), respectively. The likelihood ratio test showed that the non-homogeneous model fitted the data better than an age-homogeneous model (P